upgrade Room-reservation system

[luisgreg99]

Descriptive summary

Options:

a) Upgrade to Rails 5:

Upgrading to Rails 5 can resolve this issue #355

In order to resolve #355, I tried to upgrade to gem 'sass-rails', '~>6.0', and I found that it also requires at least sprockets 3.7.2. I pushed the update in this branch upgrade/sass-rails-from-2-to-6 for testing.

It looks like sass-rails should be automatically updated to 6 with #354, which was recently posted by GitHub dependabot. This updates sass-rails to 6 and sprockets to 4, but it also does a rails upgrade from 4.2.11 to 5.2.4.1. I think #354 should resolve this update, but it needs additional changes since rails 5 requires these updates to the codebase to bump to rails 5: https://edgeguides.rubyonrails.org/upgrading_ruby_on_rails.html#upgrading-from-rails-4-2-to-rails-5-0

b) Rebuild with latest rails

Related work

#355